"Danny D." wrote:

I can't understand HOW it works given that it's at the top of a hill.

At that height above the house, no water is ever going to flow backward
into the water supply (I think).

The only water higher is the water tank itself, the bottom of which is at
the same level as this Wilkins Zurn water check valve.

I don't know WHY this check valve even exists, since it's 10 to 20 feet
ABOVE almos all the spigots (except those at the water tank itself).

Do you agree I can just bypass this check valve?
Or am I missing something obvious?

Yes, you are missing something obvious. If there is no check valve there, water
can be drawn by vacuum back into the house. The elevation of the line is
immaterial.